1 - This was the second attempt to drill a well in about the same spot. The first well had to be abandoned because the well had been drilled too fast (under pressure from BP to bring the well in quickly). Result: the rock fractured, causing loss of control of pressure in the well. Twenty-five million bucks down the drain, said BP to the crew. So they had to try again, in a rock formation known to be problematic.
2 - Early on while drilling the second well (the one that eventually blew up) an accident damaged part of the blowout preventer (BOP). According to Williams, they were conducting a routine test of the annular, a ring of rubber that closes around the well at the top of the BOP stack. While the annular was closed, thus closing off the well, a driller accidentally pushed a joystick, which pulled the pipe casing up through the rubber seal at very high pressure. A short time later, after drilling had resumed, pieces of rubber began coming up from the bottom of the well. A drilling supervisor told Williams that the rubber debris was "no big deal".
3 - The BOP has two redundant electronics boxes, called pods, which communicate with the surface. These are critical devices which trigger the BOP to close the well in emergency. One of the two pods was problematic and occasionally inoperable. The batteries on the BOP were also weak.
4 - The well was in the process of being closed with cement plugs when the blowout occurred. The day of the blowout, there was a disagreement between the Transocean supervisor and the BP supervisor over how that should be accomplished. The Transocean guy wanted to keep mud in the well (i.e., keep pressure in the well) during the cementing. The BP guy wanted the mud pulled from the well for cementing, because it was faster and they were already behind schedule. The BP guy won the argument. If pressure had been maintained in the well during the cementing operation, the blowout would not have occurred.
From another forum posted from another forum:
BP contracted Schlumberger (SLB) to run the Cement Bond Log (CBL) test that was the final test on the plug that was skipped. The people testifying have been very coy about mentioning this, and you'll see why.
SLB is an extremely highly regarded (and incredibly expensive) service company. They place a high standard on safety and train their workers to shut down unsafe operations.
SLB gets out to the Deepwater Horizon to run the CBL, and they find the well still
kicking heavily, which it should not be that late in the operation. SLB orders the"company man" (BP's man on the scene that runs the operation) to dump kill fluid down the well and shut-in the well. The company man refuses. SLB in the very next sentence asks for a helo to take all SLB personel back to shore. The company man says there are no more helo's scheduled for the rest of the week (translation: you're here to do a job, now do it). SLB gets on the horn to shore, calls SLB's corporate HQ, and gets a helo flown out there at SLB's expense and takes all SLB personel to shore.
6 hours later, the platform explodes.